Knowing Israel can destroy their nuclear sites will deter Iran from trying to produce a nuclear weapon.
US President Joe Biden’s administration seeks to negotiate with Iran. If it does not work, the US will have to deter Iran from producing nuclear weapons. Another scenario is that the 2015 nuclear agreement with Iran, the Joint Comprehensive Plan of Action, might survive and even be improved following future negotiations.
It would include strict monitoring of Iran’s nuclear program, but this will not be sufficient. Deterrence will also be required. Negotiations will deficiently be needed when the JCPOA expires – or even before that if Iran assumes it has the opportunity to produce the bomb. This could happen if the US is deeply busy with a major crisis somewhere, such as with China. Either way deterrence, based on boosting Israel’s military capabilities, should be part of the effort to make sure Iran does not try to produce a nuclear weapon